Biotechnology Department, Federal University of Lavras, Lavras, Brazil.
Embrapa Maize and Sorghum, Sete Lagoas, MG, Brazil.
Neotrop Entomol. 2022 Dec;51(6):869-876. doi: 10.1007/s13744-022-00996-1. Epub 2022 Oct 10.
The first step for biological insecticide production is the evaluating of the pathogenicity and strains virulence of entomopathogens against the target pests. Bacillus thuringiensis (Bt) is widespread in nature, lethal pathogen of a range of orders and the most widely used entomopathogenic biological control agent. Therefore, our objective was to study the susceptibility of six important lepidopteran pests in Brazilian agricultural production systems, Anticarsia gemmatalis (Hübner), Chrysodeixis includens (Walker) Helicoverpa armigera (Hübner), Spodoptera cosmioides (Walker), S. eridania (Cramer), and S. frugiperda (Smith), to Bt strains. In vitro bioassays were conducted with neonate larvae exposed to two Bt strains, 1680A and 775E, in seven concentrations of spores and protein crystals. After 7 days, the mortality was evaluated and indicated that lethal concentration (LC) for 775E strain ranged from 7.72 × 10 to 2.45 × 10 spores mL and for 1608A strain from 5.63 × 10 to 1.21 × 10 spores mL. The strain 1608A was more toxic for A. gemmatalis and H. armigera than 775E strain, and then was further evaluated in greenhouse bioassays with maize and soybean plants infested separately with target insects. The strain 1608A showed an efficient control for most insect species studied in the greenhouse bioassays, promoting considerable reduction in leaf injury and demonstrating a high potential in biological control of important lepidopteran species in crop production systems in Brazil.
生物杀虫剂生产的第一步是评估昆虫病原对目标害虫的致病性和菌株毒力。苏云金芽孢杆菌（Bt）广泛存在于自然界中，是一系列目昆虫的致死病原体，也是应用最广泛的昆虫病原生物防治剂。因此，我们的目标是研究巴西农业生产系统中六种重要鳞翅目害虫对 Bt 菌株的敏感性，包括 Anticarsia gemmatalis (Hübner)、Chrysodeixis includens (Walker)、Helicoverpa armigera (Hübner)、Spodoptera cosmioides (Walker)、S. eridania (Cramer) 和 S. frugiperda (Smith)。采用离体生物测定法，用接触两种 Bt 菌株 1680A 和 775E 的初孵幼虫，在 7 个孢子和蛋白晶体浓度下进行实验。7 天后，评估死亡率，结果表明 775E 菌株的致死浓度（LC）范围为 7.72×102.45×10 个孢子/mL，而 1608A 菌株的致死浓度（LC）范围为 5.63×101.21×10 个孢子/mL。菌株 1608A 对 A. gemmatalis 和 H. armigera 的毒性比 775E 菌株更强，然后在温室生物测定中用玉米和大豆植株分别感染目标昆虫进行进一步评估。在温室生物测定中，菌株 1608A 对大多数研究的昆虫物种表现出高效的控制作用，显著减少叶片损伤，在巴西作物生产系统中对重要鳞翅目物种的生物防治具有很大的潜力。
